The increasing sampling capabilities of emerging surveillance, communication, and imaging systems (such as the wide area airborne-motion imaginary units, future satellite technologies, and millimeter-wave (mm-wave) imaging systems) necessitate high-gain antennas with wide-field-of-view (WFoV) beam steering capabilities. The antenna components of these systems are traditionally implemented with reflectors, lenses, and phased arrays.
Reflector antennas are typically not attractive as they are bulky and require a very precise mechanical elevation/azimuth scan over a WFoV at mm-waves. Microwave lenses, on the other hand, can be lightweight and compact. However, conventional designs generally suffer from low-scan volumes. More importantly, high-gain WFoV beam scanning typically requires a complicated radio frequency (RF) switch matrix and power divider implementations to accommodate tightly packed receive/transmit arrays at the focal plane. Phased antenna arrays offer important advantages over reflectors and lenses because they can potentially provide low-profile and high-efficiency apertures due to the absence of spill-over losses. However, for high-gain mm-wave apertures, their advantages are accompanied by high system complexity and cost. For example, a 30 GHz Ka-band ideal-phased array with 100% aperture efficiency can require an aperture size of 9×9 cm2 to deliver 30 dB directivity. If realized from half-wavelength spaced antenna elements, the phased array may require 18×18 (i.e., 324) antennas and a substantial amount of hardware in the form of phase shifters and power dividers.
From the above discussion, it can be appreciated that it would be desirable to have practical and low-cost implementations of beam scanning antennas that meet the demanding needs of high gain and WFoV. Such implementations hold promise to transform the use of high data rate surveillance, communication, and imaging systems from specialized needs into mainstream technologies.